Method for producing polymer-free area on a substrate

ABSTRACT

The invention relates to a method for producing a polymer-free area, characterized by applying at least one peelable layer to the substrate, and/or to one or more polymer layer(s) situated on the substrate, in those areas where a polymer-free area is formed on the substrate by removing the peelable layer. The invention thus provides a method for producing polymer-free bonding areas or, by placing a diode-protecting cap on the polymer-free area of the substrate, a hermetically sealed connection between the substrate and the diode-protecting cap.

[0001] The invention relates to a method for producing a polymer-free area on a substrate, the use of a peelable layer to produce polymer-free areas on a substrate as well as a product manufactured according to this method.

[0002] Numerous methods for producing organic light-emitting diodes (OLEDS) are known from the related art. For example, methods and suitable materials for producing organic light-emitting diodes (OLEDs) are described in Philips Journal of Research, Vol. 51, No. 4,461 (1998).

[0003] Conventional OLEDs are made up of a plurality of organic polymer layers that are situated on a substrate, glass, for example. In order to ensure an adequate life of such OLEDs, a hermetically sealed encapsulation of the OLED is required because calcium in particular, but also the polymers, react with oxygen and water so that signs of degradation frequently occur in customary OLEDs, which significantly reduce the life of such OLEDs.

[0004] In the related art, the individual polymer layers are applied to the diode using a spin coating process by distributing polymer solutions homogeneously over the entire substrate surface. In the last procedural step, a glass cap is cemented to the topmost polymer layer situated on the substrate as a protection. However, the bond of polymer layers to glass is not adequate to ensure a permanent cementing of the glass cap. In the least favorable case, the polymer layer acts as a separating agent to a certain degree, making it impossible to cement the glass cap onto the polymer layer.

[0005] Another disadvantage is that the polymer layers form undesirable diffusion paths for water and oxygen because they are located in the glue joint of the glass cap. Finally, polymers can be solubilized by adhesive, as a result of which the curing reaction of the adhesive may be adversely affected.

[0006] If, as an alternative to this, the polymer layers are removed mechanically by scraping or are ablated at the appropriate locations on the substrate using laser radiation to produce a glass-glass connection between the glass cap and the glass substrate, this results in the production of particles that can damage the OLED. Moreover, laser ablation is too slow and too costly for industrial applications with high throughput.

[0007] The object of the present invention is to overcome the disadvantages in the related art and to provide a method that makes hermetically sealed packaging of a diode possible in a reproducible manner.

[0008] The object of the present invention is achieved by a method through which a polymer-free area is produced on a substrate, at least one peelable layer being applied to the substrate and/or to a polymer layer situated on the substrate at the places at which a polymer-free area is formed by removing the peelable layer.

[0009] XPS studies show that, with the method of the present invention, removing the peelable layer creates residue-free, polymer-free areas.

[0010] Applying a diode-protective cap on the polymer-free area of the substrate makes it possible to form a hermetically sealed connection, preferably a hermetically sealed glass-glass connection, between the substrate and a diode-protective cap. According to the present invention, it is also possible to place a plurality of diodes (=displays) under one diode-protective cap. The components may be individualized after the encapsulation, i.e., after joining the protective cap or cover to the substrate.

[0011] The hermetically sealed connection of the diode-protective cap to the substrate may be produced physically and/or chemically using adhesive. Preferred adhesives include, for example, light curing epoxy resins. They may be applied by dispensing or screen printing.

[0012] The diodes hermetically encapsulated according to the present invention, such as OLEDs, have high stability in storage, and pass 85/85 tests in a reproducible manner, i.e., storage at 85% relative humidity and a temperature of 85° C.

[0013] In addition, it is possible to produce polymer-free bonding areas on the substrate, a diode substrate, for example, using the method of the present invention by applying the peelable layer at the places on the diode substrate where bonding takes place.

[0014] The substrate and the diode-protective cap are preferably made of glass, such as soda-lime glass, ceramic and/or polymer. It is preferred that the diode-protective cap and the substrate have identical coefficients of expansion.

[0015] The following combinations are preferred: Substrate Diode-protective cap Glass Glass Glass Substrate-polymer Substrate-polymer Glass Substrate-polymer Substrate-polymer

[0016] Films in particular, preferably made from the materials named above, may be used for the diode-protective cap and/or the substrate. Suitable substrate-polymer films preferably include polyethylene terephthalate, polyethylene, polyether sulfone and/or polyether ketone. The substrate polymers in this case are not included in the term “polymer-free,” which is produced by pulling off the peelable layer.

[0017] The thickness of the substrate and of the diode-protective cap customarily ranges between 0.5 mm-2 mm. However, it may also be <0.5 mm or >2 mm.

[0018] Preferably the area of the substrate is in the range 5×5 mm²-150×150 mm². However, it may also be <5×5 mm² or >150×150 mm². The protective cap may cover the substrate completely or incompletely.

[0019] Customarily, the substrate has an anode, preferably an indium tin oxide anode on at least one surface side and the light-emitting layer has a cathode, preferably a Ca cathode.

[0020] The peelable layer may be used in different ways. In one case, it may be used, for example, as a protective layer, i.e., corresponding substrate places at which the peelable layer is present, are not covered by the polymer during the spin coating and/or the underlying polymer layer(s) is/are removed when the peelable layer is pulled off. The peelable layer may also be used to pull off a polymer layer or layers located below it along with it. To this end, it is applied to the polymer layer at the appropriate places or areas to be removed. The peelable layer is distinguished in that the polymer component to be removed bonds to it better than to the substrate/the protective cap from which it is to be removed.

[0021] The peelable layer(s) may be applied by sputtering, by brushing, using a dispenser or by screen printing, the areas on the substrate onto which the peelable layer is to be applied preferably being defined using a template.

[0022] The peelable layer may be formed from a water-based polymer dispersion and/or from an organic polymer solution, the peelable layer preferably being based on a rubber including gutta percha, nitrile rubber, polyisoprene, polybutadiene and/or polyisobutylene. After drying on a substrate, these dispersions or solutions produce an elastic film, which may be pulled off the substrate surface in a simple manner without breaking down or tearing.

[0023] The peelable layer is customarily dried in a temperature range of 20° C.-100° C.

[0024] The thickness of the peelable layer is preferably ≦1 μm-≧100 μm, preferably 5 μm-80 μm, more preferably 10 μm-60 μm and still more preferably 20 μm-50 μm. The peelable layer may be removed by pulling off and/or by vacuum, for example, using a vacuum sealing lip either in its entirety or only in part.

[0025] The polymer layer(s), which according to the present invention, may be removed at least in areas using the peelable layer, may be one or a plurality of diode layer(s), a hole conduction layer in particular of PEDOT or polyaniline, for example, an emitter layer of polyfluorene or a poly(p-phenylenevinylene) derivative and/or an electron conduction layer of polybenzoxazole, for example.

[0026] A preferred embodiment of the present invention relates to a hermetically sealed encapsulated diode having a protective cap, preferably an OLED, on a substrate, which may be manufactured according to the method of the present invention.

[0027] Another preferred embodiment has a substrate on which a diode having an ITO anode, an HTL layer, an emitter layer, an ETL layer and a cathode is situated, the diode being hermetically encapsulated on the substrate.

[0028] Preferred embodiments of the method of the present invention according to the preamble of claim 1 will be explained below in greater detail with reference to FIGS. 1 and 2.

[0029]FIG. 1 shows a substrate having a peelable layer and a spin coating layer.

[0030]FIG. 2 shows a substrate having a polymer layer and a peelable layer applied to it.

[0031] The invention will be explained in greater detail with reference to the following examples 1-2.

EXAMPLE 1

[0032] A peelable frame as a protective frame for the substrate surface is produced on a glass substrate, on which the OLED is built up, at the places where a glass-glass sealing connection is to be produced later. Preferably a latex protective coating is used for this purpose. The application is performed manually using a template. The thickness of the peelable layer is selected in such a way that a subsequent spin coating process is not adversely affected. Advantageously the layer thickness is in the range from 10-100 μm. In the case that glass protective caps are cemented, the cap geometry determines the geometry of the peelable frame. In the present case, it is a rectangle of edge lengths 20×40 mm and a width of 2 mm. After the peelable layer has dried, which may take place at room temperature or a higher temperature, a PEDOT solution is applied by spin coating at 2000 rps for 20 seconds. After briefly drying this layer, the peelable layer is pulled off. As a result, a polymer-free frame having an edge length of 20×40 mm and a width of 2 mm having sharp edges and corners is obtained on the glass substrate (see FIG. 1). The PEDOT layer is now dried at 200° C. for 2 minutes.

EXAMPLE 2

[0033] A polyfluorene layer is applied to the substrate obtained according to example 1 by spin coating from a xylene solution at 2000 rps for 20 seconds, for example. After the polymer layer has started to dry, the peelable frame is again applied congruently to the PEDOT-free area of the substrate of the peelable frame. A latex protective coating is used for this purpose. The application is performed by hand, for example, using a template. After the peelable frame has dried at room temperature or at a higher temperature, the peelable frame is pulled off. In doing so, the polyfluorene layer located under it is pulled off with it because of the bond to the peelable frame. As a result, a polymer-free frame having an edge length of 20×40 mm and a width of 2 mm having sharp edges and corners is obtained. In the area of this frame, it is now possible to produce a hermetically sealed glass-glass connection, in the present case by cementing a glass protective cap using a light curing epoxy resin based adhesive. Before cementing, a calcium layer of a thickness of 100 μm is applied as a cathode by vacuum metallization. 

What is claimed is:
 1. A method for producing a polymer-free area on a substrate, wherein at least one peelable layer is applied to the substrate and/or to a polymer layer(s) situated on the substrate at the places at which a polymer-free area is formed on the substrate by removing the peelable layer.
 2. The method as recited in claim 1, wherein the polymer layer(s) is (are) a diode layer, preferably a hole conduction layer, an electron conduction layer and/or an emitter layer.
 3. The method as recited in claim 1 or 2, wherein a hermetically sealed connection is produced between the substrate and a diode-protective cap situated on it by placing the diode-protective cap on the polymer-free area of the substrate.
 4. The method as recited in one of the preceding claims, wherein polymer-free bonding areas are produced on the substrate by applying the peelable layer at the places on the substrate where bonding takes place.
 5. The method as recited in one of the preceding claims, wherein the peelable layer(s) is (are) applied by spraying, by brushing, by a dispenser or by screen printing, a template preferably being used for spraying and brushing.
 6. The method as recited in one of the preceding claims, wherein the peelable layer is formed from a water-based polymer dispersion and/or from an organic polymer solution, the peelable layer preferably being based on a rubber including gutta percha, nitrile rubber, polyisoprene, polybutadiene and/or polyisobutylene.
 7. The method as recited in one of the preceding claims, wherein the peelable layer is removed by vacuum.
 8. The method as recited in one of the preceding claims, wherein the hermetically sealed connection of the diode-protective cap to the substrate is produced physically in the polymer-free area and/or chemically using adhesive.
 9. The method as recited in one of the preceding claims, wherein the diode-protective cap and/or the substrate is comprised of glass or substrate polymer.
 10. The method as recited in one of the preceding claims, wherein the diode-protective cap and the substrate have identical coefficients of expansion.
 11. The method as recited in one of the preceding claims, wherein a plurality of diodes is situated under one diode-protective cap.
 12. A use of the peelable layer as recited in one of the preceding claims to produce polymer-free areas on one substrate.
 13. The use of the peelable layer as recited in claim 12 to produce a hermetically sealed connection between the substrate and a diode protective cap situated on it by placing the diode protective cap on the polymer-free area of the substrate.
 14. The use of the peelable layer as recited in claim 12 to produce a polymer-free bonding area on the substrate by applying the peelable layer at places on the substrate where bonding takes place.
 15. A product that may be produced according to the method as recited in one of claims 1 through
 11. 16. The product as recited in one of the preceding claims including at least one substrate, at least one peelable layer which is suitable for producing polymer-free areas on the substrate and, if necessary, at least one diode, preferably an organic light-emitting diode. 